1. Field of invention
This invention is related generally to an angle measuring instrument, and more particularly to a inclinometer of the type having a casing, a scale disposed within the casing and a locking device.
2. Description of prior art
Inclinometer can measure the angle between an object and a vertical line in the vertical plane. When using the inclinometer measuring the angle between two objects in a vertical plane, most of the time you have to measure the angles between the objects and vertical line, then calculate the two angle to get the angle between the two objects. It is very inconvenient to use that method. U.S. Pat. No. 4,656,752 discloses a precise-reading angular level that includes a casing, and a rotational protractor rotationally mounted in the casing, a plumbing swing angle indicator pivotally mounted in the casing. By using this device, the user can measure the angle between two objects with one measurement, but still has to manually adjust the inclinometer to zero before making the measurement. That method is inconvenient and may not be accurate due to the error made by manually adjusting it to zero.